1 files changed, 47 insertions, 0 deletions
diff --git a/keystone/openstack/common/local.py b/keystone/openstack/common/local.py
new file mode 100644
index 00000000..e82f17d0
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+++ b/keystone/openstack/common/local.py
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+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack Foundation.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Local storage of variables using weak references"""
+
+import threading
+import weakref
+
+
+class WeakLocal(threading.local):
+    def __getattribute__(self, attr):
+        rval = super(WeakLocal, self).__getattribute__(attr)
+        if rval:
+            # NOTE(mikal): this bit is confusing. What is stored is a weak
+            # reference, not the value itself. We therefore need to lookup
+            # the weak reference and return the inner value here.
+            rval = rval()
+        return rval
+
+    def __setattr__(self, attr, value):
+        value = weakref.ref(value)
+        return super(WeakLocal, self).__setattr__(attr, value)
+
+
+# NOTE(mikal): the name "store" should be deprecated in the future
+store = WeakLocal()
+
+# A "weak" store uses weak references and allows an object to fall out of scope
+# when it falls out of scope in the code that uses the thread local storage. A
+# "strong" store will hold a reference to the object so that it never falls out
+# of scope.
+weak_store = WeakLocal()
+strong_store = threading.local()